Wireless communication systems, such as GSM and the 3rd Generation (3G) of mobile telephone standards and technology, are well known. An example of 3G standards and technology is the Universal Mobile Telecommunications System (UMTS™), developed by the 3rd Generation Partnership Project (3GPP™) (www.3gpp.org).
The 3rd and 4th generations of wireless communications, and in particular systems such as LTE, have generally been developed to support macro-cell mobile phone communications. Here the ‘phone’ may be a smart phone, or another mobile or portable communication unit that is linked wirelessly to a network through which calls are connected. Henceforth all these devices will be referred to as mobile communication units. ‘Calls’ may be data, video, or voice calls, or a combination of these. An increasing proportion of communications involve data rather than voice, and the term ‘connection’ may be used for both data and voice ‘calls’.
Macro cells utilise high power base stations to communicate with wireless communication units within a relatively large geographical coverage area. The coverage area may be several square kilometers, or larger if it is not in a built-up area.
Typically, mobile communication units communicate with each other and other telephone systems through a network. In a 3G system, this is the ‘Core Network’ of the 3G wireless communication system, and the communication is via a Radio Network Subsystem. A wireless communication system typically comprises a plurality of Radio Network Subsystems. Each Radio Network Subsystem comprises one or more cells, to which mobile communication units may attach, and thereby connect to the network. A base station may serve a cell with multiple antennas, each of which serves one sector of the cell. Often a cellular wireless communication system is described as comprising two parts: the network; and the mobile communication units.
FIG. 1 provides a perspective view of one prior art wireless communication system 100. The system 100 of FIG. 1 comprises a network of base stations BS1-BS8. Only one mobile communication unit 110 is shown. In a real network, there may be anywhere from thousands to millions of mobile communication units.
A base station such as 120 communicates with mobile communication unit 110. Base station 120 allows mobile communication unit 110 to place calls through the network, and receive calls routed through the network to base station 120.
Base station 130 has been shown as having a coverage area 132. If base station 130 had an omnidirectional antenna, and the terrain was flat, then coverage area 132 might be circular. However, both the shape and extent of the coverage areas of a typical base station depend on many variables, and may change with time.
Controller 140 manages calls within the wireless communication system 100. Controller 140 would be linked to all the base stations BS1-BS8, but the links are not shown in order to keep FIG. 1 simple to interpret. Controller 140 may process and store call information from the base stations BS1-BS8, plus many other base stations not shown in FIG. 1. In a UMTS network, controller 140 may be linked to the base stations via one or more Radio Network Subsystems.
Radio networks produce data at a very high rate when controlling the operation of mobile devices. This data rapidly builds to provide a vast set of data. Some prior art systems make this set of data available for processing customer complaints. In a typical scenario, a customer will report that their mobile communication device is prone to one or more problems. These problems might be, for example, that the device suffers frequent dropped calls or only achieves low data rates. Such complaints can sometimes be resolved by manually searching through the data produced in the radio network. If this is successful, it may explain whether the mobile communication device is faulty, or whether there is a fault in network.
When there is neither a fault in the network nor in the subscriber's mobile communication device, the fault may be due to the real, physical network not corresponding to the stored map of the network held within the system itself. It may occasionally be possible to trace the problem to such a cause manually, although not all recorded faults will allow a definitive identification of such discrepancies.
When a fault is due to the real network not corresponding to the stored map of the network, the network's own ‘network configuration data’ does not match the actual set of components deployed in the real network, i.e. as the network was built or upgraded. The configuration data held by the communication network may typically originate from a sub-system called the ‘Network Planning System’. The Network Planning System is a database that holds such information as base station locations and pointing angles of sector antennas. However, the real network may have been built at slight variance to the desired configuration set out in the Network Planning System. Other sources of variance might be, for example, an antenna being knocked out of alignment. Such variances may lead to the mobile communication device experiencing sub-optimal support from the real network.
Prior art arrangements typically allow data from the network to be loaded and analysed in order to identify possible problems. However, this requires users to load and analyse the data manually to deliberately look for a discrepancy or fault, once the user has been notified that such a fault or discrepancy exists.
U.S. patent application Ser. No. 13/144,128, with filing date of 12 Jul. 2011, is entitled ‘Wireless Communication Network’. U.S. Ser. No. 13/144,128 provides a method of correcting network configuration data describing a wireless communication network. Both applications are hereby incorporated by reference in their entireties. For at least one wireless communication device communicating with at least two sectors of a wireless communication network, a probability density function is derived for a location of each wireless communication unit. The probability density function is derived from one or both of:
(i) measurement information from the wireless communication unit;
(ii) the network configuration data.
The probability density functions from multiple communications are combined to provide a combined function, which is analysed to derive a most likely value for a network parameter. This can lead to a corrected network parameter, which can in turn be incorporated into the stored network configuration data. The method may comprise calculating a confidence score for each probability density function incorporated in the combined function, and calculating the value of the combined function from the confidence scores. The analysis may comprise varying the network parameter until a maximum value for the combined function has been reached, and selecting the value of the network parameter that maximises the combined function as the most likely value for the network parameter.
Also known is a basic system of real time surveillance of a wireless communication system. This surveillance system relies on two features of wireless communication systems:
(i) The wireless communication device's ‘active set’. The active set is the list of cells or sectors that provide sufficient signal strength for the wireless communication device to consider communicating through the cell/sector. The active set is therefore the list of cells/sectors whose signal strength the mobile communication device will monitor periodically. The mobile communication device will select one of the cells or sectors from the active set, when it wishes to initiate a connection, i.e. a voice or data call, or to hand-off an on-going connection.
(ii) The network configuration data comprises a ‘neighbor cell list’. The neighbor cell list is a list of cells which are recorded in the network configuration data as being neighbors of any given cell.
In this surveillance system, a radio network controller (RNC) waits for a message from a mobile communication device, indicating that the mobile communication device has located a neighboring cell that appears to be strong enough to be added into the current ‘active set’ of the wireless communication device. The RNC then checks the neighbor cell list for the wireless communication system, to see if the neighbor cell list includes the neighboring cell identified by the mobile communication device. If it does, then the RNC allows the mobile communication device to add the neighboring cell to the mobile communication device's active set.
However, if the neighbor cell list does not show an entry corresponding to the neighbor cell detected by the mobile communication device, then the RNC can generate an alarm or message saying that there is a missing neighbor. This is a simple system, which assumes that each neighbor cell detected by any mobile communication device ought to be in the neighbor cell list held in the Network Configuration Data. This surveillance method therefore defaults to a conclusion that the neighbor cell list is in error. Another shortcoming of this approach rests in the fact that it involves waiting for certain messages that do not then result in changes to the radio configuration, e.g. the adding of another sector into the active set of the mobile communication device. Such passive waiting may mean that there has been an unrecognised problem in the network for some time, before any notification of the potential problem reaches the RNC. The unrecognised problem, for however long it lasts prior to identification and correction, will mean poorer service for users of the network and potentially extra demand in other parts of the network and poorer throughput data rates for the users.
Hence, there is a need for an improved method for verifying stored network configuration data in a wireless communications network with a cellular network, such as an LTE, GSM or UMTS network.